Living with Floods

Flooding in Newcastle

Flooding is a natural process caused by heavy rainfall. It has helped to shape the landscape around us, the creeks and swamps, and the floodplain on which much of Newcastle has been developed.

Flooding is generally a rare event but will continue to happen into the future. It is not possible to predict when, where, or how big the next flood will be. We can, however, estimate the likelihood of different sizes of floods and prepare for the next big flood before it arrives.

Flood Frequency

Commonly the 100 year flood is referred to when undertaking floodplain management even though there is actually no such thing as a '100 year flood'. Each flood is different. On average, larger floods are rarer than smaller floods and the chance of a certain size flood happening in any given year is the same each year, even if a flood occurred the year before. Thus the 100 year flood describes a flood that has a 1 in 100 chance of occurring annually.

The largest flood that could occur is called the Probable Maximum Flood. Newcastle has not experienced such a flood in the last two hundred years.

The prediction of floods of a given size or frequency are subject to industry standard methods outlined in Australian Rainfall and Runoff publish by Engineers Australia.

The impact of heavy rain

The impact of heavy rain will behave according to the topography in different catchment areas. In large catchments, such as the Hunter River, it takes a long time for widespread rainfall to 'fill' the catchment and come down the river. And therefore there is several days lead time for the peak of the flood in lower parts of the Hunter Valley.

In smaller catchments, including most of Newcastle's suburbs, it only takes a short time for rainfall to 'rush' down the catchment and overwhelm drainage systems causing localised flooding. This can occur in approximately 60minutes following intense rainfall and is commonly referred to as flash flooding.

Potential flood areas in Newcastle

The blue areas on the map represent the full extent of the floodplain and could flood in the future. Surprisingly many of these areas are in the suburbs away from the Hunter River Floodplain.

Flooding Issues

There are many complex issues surrounding flooding in Newcastle including:

No effective warning for flash flooding

Low community awareness

The large numbers of properties that are at risk

The effects of past and future development

Existing development being in areas that should not have been developed

Integration with social, environmental, economic and planning issues

What areas should not be developed in the future?

What are the community's aspirations and priorities?

Concerns about potential impacts on property values.

It is critical that flood management decisions are based on realistic understanding of all possible future flooding in Newcastle.

Computer simulations of future flooding have been developed across the city. These simulations are based on the best available information of rain that can occur, tide and ocean levels, and accurate ground levels. Simulations are checked against records of previous flooding in Newcastle.

Moving Forward

Council is working on solutions to manage Newcastle's complex flooding problems with substantial grant assistance from the NSW Government. The solutions were investigated through preparation of Floodplain Risk Management Studies and Plans. A result of this work has been the adoption of Floodplain Risk Management plans for the City as a whole and more specifically in Wallsend.

Funding sources for carrying out the actions outlined in the plans is limited and subject to a range of selection criteria for projects across the state. The Council's Flood Risk Management Committee is developing strategies and action plans to live with the risks in a way that balance environmental, social and economic issues.

The committee includes Council, community and government representatives and it is taking an overall approach that:

Considers the consequences of all future flooding, from small to large floods

Investigates a number of solutions to reduce flood risk that do not rely on structural works alone, for example it may be the case that emergency management and community education strategies are implemented as the most effective solutions.

Links

Council's webpage – Flooding Section

Floodplain Management Association

National group comprising members from local councils, state government departments, insurance industry and engineers who convene to share information and lead discussion regarding floodplain management and how to guide the most appropriate methods of reducing flood risk.

State Emergency Service

The lead combat agency in case of flood and provides flood education for the community. The SES offers important information on improving awareness, preparedness and response on their website and various education efforts.